The present invention relates to power tools, and more specifically to air filters used in combustion gas-powered tools.
In the construction industry, when power tools are used in the field, on construction sites and in remote areas, tools having a self-contained source of power are preferred. One example of a self-contained source of power is a combustion engine housed within a tool. Such tools are known as combustion-powered tools or combustion tools.
Combustion tools are known in the art, and are described in U.S. Pat. Re. No. 32,452, and U.S. Pat. Nos. 4,522,162; 4,483,473; 4,483,474; 4,403,722; 5,197,646; 5,263,439 and 6,145,724, all of which are incorporated by reference herein. Similar combustion-powered nail and staple driving tools are available commercially from Illinois Tool Works of Glenview, Ill.
Such tools incorporate a tool housing enclosing a small internal combustion engine. The engine is powered by a canister of pressurized fuel gas, also called a fuel cell. A battery-powered electronic power distribution unit produces a spark for ignition, and a fan located in a combustion chamber provides for both an efficient combustion within the chamber, while facilitating processes ancillary to the combustion operation of the device. Such ancillary processes include: inserting the fuel into the combustion chamber; mixing the fuel and air within the chamber; and removing, or scavenging, combustion by-products. The engine includes a reciprocating piston with an elongated, rigid driver blade disposed within a single cylinder body.
A valve sleeve is axially reciprocable about the cylinder and, through a linkage, moves to close the combustion chamber when a work contact element at the end of the linkage is pressed against a workpiece. This pressing action also triggers a fuel-metering valve to introduce a specified volume of fuel into the closed combustion chamber.
Upon the pulling of a trigger switch, which causes the spark to ignite a charge of gas in the combustion chamber of the engine, the combined piston and driver blade is forced downward to impact a positioned fastener and drive it into the workpiece. The piston then returns to its original or pre-firing position, through differential gas pressures within the cylinder. Fasteners are fed magazine-style into the nosepiece, where they are held in a properly positioned orientation for receiving the impact of the driver blade.
Oftentimes, combustion tools are used in areas of dense contaminating particulates such as concrete dust, gypsum dust and the like. An unfortunate side effect of working in such environments is that unwanted contaminating particles regularly gum up and jam the moving parts of the tool and make it inoperable relatively early in its life cycle. Typical tools using combustion power are nail guns, concrete pin guns, screw guns, and the like.
Foam filters have previously been implemented in an effort to reduce the amount of unwanted particles gumming up and jamming moving parts within a tool. Although foam filters provide ample airflow, they are often too thin and do not allow for sufficient directional changes of airflow. Consequently, deflection opportunities for contaminating particulates are often insufficient. Moreover, the pores in these filters are too large and often do not trap tiny particulates of ten microns or less. Filters having smaller pores that trap ten-micron particulate have also been used. These filters, however, clog quickly, restrict airflow, and inhibit combustion tool operation.
Other prior art filters used in combustion tools include sponge filters and pleated filters. Sponge filters allow contamination to pass into the internal parts of the engine and cause premature failure. Pleated filters are relatively expensive compared to foam and sponge filters and also require frequent replacement.